U.S. Pat. No. 3,636,672 (Fink) purports to disclose a snap-in jamb anchor comprising a right angular bracket having a horizontal wedging plate arranged to establish a wedge-type friction fit with the interior surface of channel-shaped sheet metal doorjambs at opposite sides to provide a connection between the horizontal girder of a building and the jambs, thereby to support the door frame within an opening of a sheet metal wall. Jamb extensions may be secured to a vertical flange of each jamb anchor and extend upwardly above the header of the door frame to a roof girder which is located above the header so as to act in combination with the jamb anchors in stabilizing the upper portion of the metal door frame within its opening.
U.S. Pat. No. 4,539,784 (Allen) purports to disclose an adjustable device for anchoring door jambs of various sizes in a fast and efficient manner. The device includes one or more frame members which receive a pair of overlapping L-shaped planar members in sliding engagement with each other. Each frame member is generally of an L-shaped configuration having vertical and horizontal planar portions, and with a lip formed along the outer edge of the horizontal portion to provide a slot for use in retaining the overlapping members. The overlapping members each have vertical and horizontal planar portions, with the horizontal portions being of sufficient length to allow the length of the overall anchor to be varied by slidably positioning the overlapping members relative to each other. The position of each frame member relative to the overlapping members can also be adjusted to correspond with the shape and construction of a particular door jamb.